ornate bichir fish

This is probably how fish evolved to walk on land

Researchers are using a living fish, called Polypterus, to help show what might have happened when fish first tried to walk out of the water.

Polypterus is an African fish that can breathe air, “walk” on land, and looks much like those ancient fishes that evolved into tetrapods.

About 400 million years ago, a group of fish began exploring land and evolved into tetrapods—today’s amphibians, reptiles, birds, and mammals. But just how these ancient fish used their fishy bodies and fins in a terrestrial environment and what evolutionary processes were at play remain scientific mysteries.

The team of researchers raised juvenile Polypterus on land for nearly a year, with the aim of revealing how these “terrestrialized” fish looked and moved differently.

“Stressful environmental conditions can often reveal otherwise cryptic anatomical and behavioral variation, a form of developmental plasticity,” says Emily Standen, a former McGill University postdoctoral student who led the project, now at the University of Ottawa.

“We wanted to use this mechanism to see what new anatomies and behaviors we could trigger in these fish and see if they match what we know of the fossil record.”

On their fins

As reported in Nature, the fish showed significant anatomical and behavioral changes. The terrestrialized fish walked more effectively by placing their fins closer to their bodies, lifted their heads higher, and kept their fins from slipping as much as fish that were raised in water.

“Anatomically, their pectoral skeleton changed to become more elongate with stronger attachments across their chest, possibly to increase support during walking, and a reduced contact with the skull to potentially allow greater head/neck motion,” says Trina Du, a McGill PhD student and study collaborator.

“Because many of the anatomical changes mirror the fossil record, we can hypothesize that the behavioral changes we see also reflect what may have occurred when fossil fish first walked with their fins on land,” says Hans Larsson, Canada Research Chair in Macroevolution at McGill.

The terrestrialized Polypterus experiment is unique and provides new ideas for how fossil fishes may have used their fins in a terrestrial environment and what evolutionary processes were at play.

Larsson adds, “This is the first example we know of that demonstrates developmental plasticity may have facilitated a large-scale evolutionary transition, by first accessing new anatomies and behaviors that could later be genetically fixed by natural selection”.

The Canada Research Chairs Program, Natural Sciences and Engineering Research Council of Canada (NSERC), and Tomlinson Postdoctoral fellowship supported the work.

Source: McGill University

chat6 Comments


  1. Scuttlefish

    I just can’t picture why creatures would have evolved skeletons in water. Jelly fish are perfectly adept without them.Perhaps the first creatures on the shore did not have skeletons. Creatures without skeletons could have washed up onto the shore, and the ones that survived were those that could maneuver (and procreate) on the shore and the water, Their progeny, the second generation, could have returned to the water with new strengths ( a skeleton that could defy gravity and fins for pulling themselves through water or land) that made them very successful. Some of their progeny, the third generation, could have returned to shore and been the ancestors of the tetrapods. Maybe another tree existed of land creatures that evolved from the first group washed ashore.

  2. Joseph Fakhoury

    All this is hypothetical. How does a living organism evolve? Does it will its evolution. The fish thought to themselves why not attempt a walk on the shore…. and that was it . What would have induced the fish to go for a stroll? Scarcity of food in the sea or maybe conditions were getting to cold in the water!!!.. Man has always dreamed of flying. Do you suppose that if primitive man kept emulating flying creatures he would to day have flying humanoids. So from the see life in its diversity was created!!! I guess , based on the time scale, man in a hundred million years may develop winged arms that allow him to fly about!!!

  3. Earthcitizen

    @”Joseph Fakhoury February 19, 2015″

    No organisms do not “will evolution” nor will man “will wings” in a million billion years. For the simple reason our brains have provided humanity with the ability to fly using mechanical means. There is no survival advantage to humans developing wings, quite the opposite, it would be a disadvantage growing and maintaining them.

  4. Earthcitizen

    “@Scuttlefish October 7, 2014”

    There is a physical limit to the size of jellyfish. Skeletons would be needed to support larger sized bodies. Once developed, skeletons became widespread in the sea and then spread to land.

    Sea organisms could have been accidentally hurled to land by tides and then had to be mobile to escape back to the sea. Those that did this best survived and increased in number. Then one day some would have made a behavioural decision to move to land after they had already acquired mobility on land.

  5. Danfu

    Professor Richard Dawkins got it wrong on how reptiles could have been evolved out of water on to land….fish has not evolved 400 million years ago yet…Ask me why?

  6. Gnollrunner

    Polypterus can indeed nearly walk. I used to keep several species of them for many ears. They are good aquarium fish although they can be a bit reclusive at times.

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